In general, a method of extracting natural salt by bringing seawater into a salt field and then drying (evaporating) the seawater is generally used to produce salt. In other words, salt is obtained by drawing seawater into a substantially rectangular retention pond with a tiled, plastic, or ceramic ground, allowing the seawater to be naturally evaporated by sunlight to deposit salts on the ground, and collecting common salt and natural salt remaining after evaporating the seawater. The natural salt or common salt extracted by evaporation of seawater contain magnesium and small amounts of various minerals, so they are known as being healthy for human.
However, according to the method of producing salt by bringing and evaporating seawater in a salt farm, salt is produced through a process whereby seawater brought into substantially retention ponds continuously installed evaporates while sequentially flowing over the retention ponds. Further, the method of producing salt from seawater requires a relatively wide area for a salt farm, considering the evaporation speed of seawater. Accordingly, it is difficult to construct a salt farm within a limited site in some cases and it becomes more difficult to ensure salt sites due to coastal development. Further, it is difficult to suddenly increase retention ponds when there is a large demand and suddenly decrease retention ponds when there is a small amount of demand due to the limited salt sites. Therefore, it is inefficient to manage productivity of salt and the salt productivity (output per unit time) is decreased by reduction of evaporation speed of seawater.
Meanwhile, there is a method of hanging evaporation sheets (diapers) on ropes in several steps to increase the evaporation rate of seawater by increasing surface areas and of installing a hoist on top to move up/down the evaporation sheet blocks and increase the density of seawater in a retention pond at the bottom.
However, according to this structure for evaporating seawater, resistance is increased when it is a windy day, so the equipment (including the evaporation sheets) is damaged. Further, if the structure for evaporating seawater is small, it does not matter, but when it is large, the evaporation sheets are blown and damaged by strong wind such as in a typhoon. Therefore, the structure cannot be constructed in a large size.
It is possible to reduce the evaporation time of seawater as much as possible by increasing the evaporation efficiency by exposing seawater to sunlight and air and allowing the seawater to move. In order to effectively evaporate seawater by spraying the seawater to evaporation ropes, it is required to make the seawater flow down. Therefore, there is a strong need for a configuration that can maximize evaporation efficiency by making seawater flow down and minimize salt production time by installing a plurality of three-dimensional seawater evaporation members in a plurality of seawater evaporation fields.